On the 'Moscow-zero' problem

The article on the zero-charge problem known as the 'Moscow zero' is a contribution to the book commemorating the sixtieth birthday of E.S. Fradkin. The article falls into three sections. The first contains a typical quantum field interpretation of the Moscow zero and related problems set against the historical background. Many-body theory offers a good opportunity for considering the Moscow zero, with macroscopic physics providing a standpoint for a better physical understanding of the problem and highlighting those aspects which might otherwise remain unnoticed. This forms the second part of the article. Finally, the third part dwells on topics in the physics of condensed media which are intimately linked with the Moscow zero and are of both general and practical interest. (author)